Federal prosecutors asked an appeals court Thursday to uphold the 2007 kidnapping convictions of a reputed Ku Klux Klan member serving three life sentences for his role in the abduction and killing of two black teenagers in Mississippi more than 40 years ago.

The full 5th U.S. Circuit Court of Appeals agreed to review the case after a three-judge panel from the court threw out James Ford Seale’s convictions last year, ruling that a statute of limitations barred him from being indicted in 2007 for the 1964 crime.

All of the court’s 18 judges heard arguments from lawyers on both sides of the case Thursday but didn’t immediately rule after the hourlong hearing, which attracted an overflow audience in the courtroom.

A Mississippi federal jury convicted Seale, now 73, of conspiring with two other unnamed Klan members to kidnap Charles Eddie Moore and Henry Hezekiah Dee, two 19-year-old friends whose decomposed bodies were pulled from a Mississippi River backwater in 1964.

Their bodies were found by investigators searching for three civil rights workers who were also killed that summer. The latter case, portrayed in the film “Mississippi Burning,” had overshadowed the disappearance of Moore and Dee.

State murder charges against Seale and another man, Charles Marcus Edwards, were brought but quickly dropped in 1964. Federal authorities revived the case in 2005, with Edwards serving as a government witness in exchange for immunity from prosecution.

Prosecutors say kidnapping was punishable as a capital crime with no time limits on prosecution in 1964. But Kathryn Nester, a public defender representing Seale, argued that a five-year statute of limitations could be applied retroactively to the 1964 case once Congress amended the federal kidnapping statute in 1972 to remove the death penalty.

“You can’t pick and choose which parts you apply retroactively … without some guidance from Congress,” she said.

Tovah Calderon, an attorney for the Justice Department’s civil rights division, argued that the 1972 amendment cannot be applied retroactively for any reason. Congress was trying to expand criminal liability for kidnapping when it made the change, she said.

“This case is about congressional intent, and in 1972 Congress did not intend to limit prosecution of anyone, including the defendant,” Calderon said.

The judges pressed Nester and Calderon to explain how other recent court rulings should govern their review of Seale’s case, but Judge Harold DeMoss Jr. suggested that this case may present new ground for the U.S. Supreme Court to explore.

“Well,” Calderon said, “we’ll go all the way (to the Supreme Court) if we have to.”